With this functionality, instead of browsing all changelists within a certain period, you can define a set of changelists to display. This is done by specifying a pair of branches in the repository (source and target), whereupon PyCharm shows only the changelists from the source branch that have been integrated into the target branch.

Additionally, you can specify various filtering options to minimize the number of extraneous changelists.

Finally, integration and managing integration status are also available directly from the Merge Info pane.